Fix Python artifact build

tools/dockerfile/grpc_artifact_python_manylinux_x64/Dockerfile

@@ -34,6 +34,19 @@ FROM quay.io/pypa/manylinux1_x86_64
 # Update the package manager
 RUN yum update -y
 
+#############################################################
+# Update Git to allow cloning submodules with --reference arg
+RUN yum remove -y git
+RUN yum install -y curl-devel expat-devel gettext-devel openssl-devel zlib-devel gcc
+RUN cd /usr/src && \
+  wget https://kernel.org/pub/software/scm/git/git-2.0.5.tar.gz && \
+  tar xzf git-2.0.5.tar.gz
+RUN cd /usr/src/git-2.0.5 && \
+  make prefix=/usr/local/git all && \
+  make prefix=/usr/local/git install
+ENV PATH /usr/local/git/bin:$PATH
+RUN source /etc/bashrc
+
 ###################################
 # Install Python build requirements
 RUN /opt/python/cp27-cp27m/bin/pip install cython

tools/dockerfile/grpc_artifact_python_manylinux_x86/Dockerfile

@@ -34,6 +34,19 @@ FROM quay.io/pypa/manylinux1_i686
 # Update the package manager
 RUN yum update -y
 
+#############################################################
+# Update Git to allow cloning submodules with --reference arg
+RUN yum remove -y git
+RUN yum install -y curl-devel expat-devel gettext-devel openssl-devel zlib-devel gcc
+RUN cd /usr/src && \
+  wget https://kernel.org/pub/software/scm/git/git-2.0.5.tar.gz && \
+  tar xzf git-2.0.5.tar.gz
+RUN cd /usr/src/git-2.0.5 && \
+  make prefix=/usr/local/git all && \
+  make prefix=/usr/local/git install
+ENV PATH /usr/local/git/bin:$PATH
+RUN source /etc/bashrc
+
 ###################################
 # Install Python build requirements
 RUN /opt/python/cp27-cp27m/bin/pip install cython